Rapaflo (silodosin)

Silodosin is a postsynaptic alpha1-adrenergic blocking agent that exhibits selectivity for alpha1A-adrenergic receptors located in the lower urinary tract (e.g., bladder base, bladder neck, prostate, prostatic capsule, prostatic urethra).

Silodosin, a trifluoroethoxy-phenoxyethyl amine derivative, is an alpha1-adrenergic blocking agent that exhibits selectivity for postsynaptic alpha1A-adrenergic receptors in the lower urinary tract (e.g., bladder base, bladder neck, prostate, prostatic capsule, prostatic urethra). Blockade of these adrenoreceptors can cause relaxation of smooth muscle in the bladder neck and prostate, resulting in improvement in urinary flow and a reduction in symptoms of benign prostatic hyperplasia (BPH). Such effects generally are achieved with silodosin dosages that do not have clinically important effects on blood pressure or heart rate.

The higher affinity of silodosin for alpha1A-adrenergic receptors in the lower urinary tract than for alpha1B-adrenergic receptors in vascular smooth muscle may result in reduced incidence of cardiovascular effects (e.g., syncope, dizziness, hypotension).

Administration of silodosin with a moderate-fat, moderate-calorie meal in 3 studies decreased AUC by 4-49% and peak plasma concentrations by 18-43%. Administration of silodosin with a high-fat, high-calorie meal was not evaluated.

Silodosin undergoes extensive metabolism in the liver via glucuronidation, alcohol and aldehyde dehydrogenases, and cytochrome P-450 (CYP) 3A4 pathways. The primary active metabolite of silodosin, KMD-3213G, is formed via uridine diphosphate-glucuronosyltransferase (UGT) 2B7-mediated glucuronidation. Another major metabolite is KMD-3293, formed via alcohol and aldehyde dehydrogenases; this metabolite is not expected to contribute substantially to the pharmacologic activity of silodosin.

Silodosin is not likely to inhibit CYP isoenzymes 1A2, 2A6, 2C9, 2C19, 2D6, 2E1, or 3A4 nor induce CYP isoenzymes 1A2, 2C8, 2C9, 2C19, or 3A4. Silodosin is also not an inducer of the P-glycoprotein transport system, but in vitro studies show that silodosin is a substrate for P-glycoprotein.

USES: Silodosin is used by men to treat the symptoms of an enlarged prostate (benign prostatic hyperplasia-BPH). It does not shrink the prostate, but it works by relaxing the muscles in the prostate and the bladder. This helps to relieve symptoms of BPH such as difficulty in beginning the flow of urine, weak stream, and the need to urinate often or urgently (including during the middle of the night).

Silodosin belongs to a class of drugs known as alpha blockers. Do not use this medication to treat high blood pressure.

Generic name: silodosin
Pronunciation: (sye-LOE-doe-sin)

The following indications are listed for Rapaflo:

• Benign Prostatic Hyperplasia With Lower Urinary Tract Symptom

Also known as: Symptomatic Benign Prostatic Hyperplasia, Symptomatic Benign Prostatic Hypertrophy, Symptomatic Bph, Symptomatic Prostatic Hypertrophy.

No ICD codes are available for this drug.